Highly viscous materials bordering between solids and fluids present special problems in mixing, refining and reacting. These materials cannot be reliably pumped, and do not follow the laws of fluids or solids flow. These materials tend to pack into any available constrained space, and tend to separate liquid from solid to form a hard solid mass if subjected to high pressure. Hence, it has been difficult to mix or refine high viscosity material reliably in a controlled way. These problems have been dealt with in my previous U.S. Pat. Nos. 2,722,163, 2,824,500, 2,978,192 and 3,221,999.
The invention involves recognition of the importance of controlling the flow of highly viscous material for mixing or refining, and devising of a simple and efficient way of controlling and varying the flow of such material as it passes through a refiner. The invention includes improved refining surfaces for a generally known cylindrical mixer-refiner having an internal rotor and a stator shell, and the improved refining surfaces are developed for optimum control of the movement and mixing of the material as it passes through the refiner to avoid packing, solid-liquid separation, and to ensure optimum and even mixing and refining.